Electron discharge device



March 11, 1958 c. 0. STALKER 2,826,712

- ELECTRON DISCHARGE DEVICE Filed Jul 19, 1954 2 Sheets-Sheet 1 FIG.

IN V EN TOR.

CH eRLES D. STALKER.

ATTORNEY Mai'ch 11, 1958 'c. D. STALKER ELECTRQN DISCHARGE DEVICE 2Sheets-Sheet 2 Filed July 19, 1954 INVENTOR.

CIZQRLES DSTALKER A TTORNE Y Ui' te 2,826,712 ELECTRON DISCHARGE DEVICEApplication July 19, 1954, Serial No. 444,135

2 Claims. (Cl. 315-523) The present invention relates to electrondischarge devices and more particularly to improvements in a reflexoscillator of the cavity resonator type as disclosed in copendingapplication Serial No. 398,321, filed December 15, 1953, by Robert S.Gormley and assigned to Bendix Aviation Corporation.

In a reflex oscillator, such as that disclosed in U. S. Patent No.2,494,693 Ekstrand et al., due to its operation at very highfrequencies, the dimensions of the critical component parts are ofnecessity small in physical size. Accordingly the concentricities andaxial alignment of the parts becomes of paramount importance. Forexample, an electron beam from a cathode .125 in diameter must befocused through gridded aperture .040" in diameter, thence throughanother gridded aperture .052" in diameter into a retarding repellerfield which returns the beam through the .052" diameter grid. Due to thefact that a portion of the electron beam current is lost throughinterception on the grid wires as it passes through the grid, it isnecessary that substantially all of the beam passes through theseapertures with as little as possible being intercepted on the edges ofthe frames supporting these grids. In addition, the retarding repellerfield must return the electrons in all parts of the beam at a given timeat substantially the same R. F. phase in order to produce the R. F.output energy. The former requires extremely accurate concentricitiesbetween component parts and the latter dictates a high degree of axialalignment of the reflector assembly. Further, service conditions requirethat the device withstand shock and vibration without failure ordegradation of the performance characteristics.

The present invention provides novel modifications for greater accuracyin locating critical component parts and to reduce critical assemblyoperations. The various modifications permit the use of simple assemblyjigs and fixtures yet accurately locate the component parts. Further themodifications increase the reliability of the tube structure, thuspermitting operation under shock and vibration conditions withoutfailure or degradation of the performance characteristics.

It is an object of the invention to provide an improved reflexoscillator of the cavity resonator type.

Another object of the invention is to provide an improved ruggedizedelectron discharge device.

Another object of the invention is to provide an improved electrondischarge device that may be readily assembled yet maintain criticaldimensions.

Another object of the invention is to provide improved and novelstructure for an electron discharge device.

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawing wherein one embodimentof the invention is illustrated by Way of example.

In the drawings:

Figure l is a sectional view to an enlarged scale of States atent anelectron discharge device illustrating an embodiment of the invention.

Figure 2 is a detailed view of the tuner support.

Figure 3 is a sectional view of the assembly shown in Figure 1 takenalong the line 3-3.

Figure 4 is a detailed view of the gun heater insulator.

Referring now to the drawing wherein similar parts in the variousfigures have been assigned the same reference numerals, the electrondischarge device therein illustrated comprises, generally, a highlyevacuated envelope and a mount fabricated of several subassem'bliesunited into an integral structure which is inserted in the envelope as aunit and supported from the sidewall thereof.

The envelope, indicated generally by the numeral 10, comprises acylindrical portion 11, which may be any suitable material such asmetal, having an outwardly extending flange 12 on one end and acounterbore portion 13 on the other end thereof. A dished base orplatform 14 is hermetically sealed to the flange .12 as will beexplained in detail later. An inverted cup shaped member 15 has anoutward extending flange 16 terminating in a cylindrical flange 17. Theflange 17 is inserted in the counterbore section 13 of the envelope 10and positioned by a shoulder 18. The member 15 is brazed to the wallsection 11 to provide a vacuum tight joint therewith. The member 15 isprovided with a central aperture in its base in which a window 19 highlytransparent to electromagnetic waves is sealed in a conventional manner.

Mounted within the enclosing vessel is a unitary assembly comprising aradio frequency unit including a reflex oscillator of the cavityresonator type and a wave guide output line or section for theoscillator, and including also a triode unit for tuning the cavityresonator. The components of this unitary assembly are built around arectangular plate 20 of a metal having high heat conductivity. The plate20 extends into and is fixed in a slot in a relatively massive coolingblock 21, also of a metal having high heat conductivity, which issecured by brazing to the wall 11 of the envelope 10 and constitutes thesupport for the unitary assembly. The block 21 is provided with recesses22 for receiving pellets of a brazing material. The plate 20 and block21 are coupled to base 14 by a pair of flexible metallic members 23, thefunction of which will appear presently.

The plate 20 is provided with a circular opening 24, defining a part ofa cavity resonator. Three pilot holes 25 are provided in the plateconcentric with the opening 24. The pilot holes 25 are located so thatpins through these holes will nest and locate the various parts. A slotor cut-out portion 26 extends from one edge of the plate 20 and having arestricted rectangular portion 27 opening into the circular opening 24,the slot defining a wave guide output section for the cavity resonator.Affixed to one face of the plate 20 is a circular, metallic frame orsupport 28 having a frusto-conical portion 29 mounting a dished orconcavo-convex grid 30 composed of fine parallel Wires. Affixed to theother face of the plate 20 is a retaining ring 31 which clamps anannular metallic diaphragm 32 to the face. The diaphragm 32 iscircularly and concentrically corrugated and mounts an annular metallicsupport or frame 33 which carries a dished or concavoconvex grid 34composed of fine parallel wires. The pilot holes 25 enable theaforementioned parts to be located with a high degree of accuracy. Pilotpins may be located in the welding electrodes, so that the parts arelocated and welded in the same fixture with the accuracy of locationbeing dependant upon the parts and tools rather than by the assemblyoperation.

The grids 30 and 34, frusto-conical support 29, diaphragm 32 and thecircular walls of the opening 24 in the plate. 21L bound a.- cavityresonator whichis tunable by flexure of the diaphragm 32.and from whichpower may be taken by Way of the restricted portion 27 of the slot orcut out portion 26: in the'plate 'and' a wave guide'35;

The Wave guide is formed of sheet metal, is of rectangularse'ctiomthroughout and t'a'p'er-s' from the cavity resonator towards thewindow"1'9-, thereby to provide a uniform impedance along its length.The guide 35 fits in the cutout'portion 26 in'the plate'zo andat itsinner end has portiOns-S'Goverlyingand-alfixed to the grid frame 28 andretaining ring 31.

At itsupper end, thewa've guide 35' is secured to" an inverted,cup-shaped metallic member 37 having an encircling fiang'e 38-toprovideachoke'joint' adjacent to the" envelope 10, thereby to-minimize'loss ofelectromagnetic energypropagatedthrough theguide 35'andWin'do'W 19. Themember 37 is secured to a cylindrical support or mount 39 having aflange 40 which is provided" with integral fingers or tabs- 41afiixed'to the pI'a'teZtY.

Cooperatively associated with the cavity resonator are an electron gunand a repeller" electrode to constitute a reflex oscillator therewith.The electron gun comprises ametallic cathode member 42'having acylindiical b'ody portion=4-3and a'dished end portion 44,the'coricav'efaceof which has'a-coatingAS ofelectronemissive' materialthereon. Disposedwith'in the cathode member 43i sa heaterelement 46',forexample; a doubl-helicaTfilament coated with aninsulating'materiallThe cathode'memb er '42is supportedwith'in a flangedcylinder 47 by.means of support wires"48locateda'teach end 'of the body. por tion 43;The support wires are of "a material'having: low heat conductivity suchas Nilvar. The cylinder47fhas a flange '49'aflixe'dtoa focusingelectrodeSlYby; Welding toan annular flange 5'1 thereon which. surrounds. a.central cylindrical portion 52. An insulator 53 is providedtosupport'the cathode heater 46. The insulator 53 (see Figure 4)'comprises'a mica strap 54 having metal tabs 55 and 56 crimped in place.The tabs 55 are used for con necting the assembly to the cylinder 47 andthe tabs 56 are used'forconnecting the heater conductors 5-7:. Thefocusing electrode 50lis secured to. an. insulating .disc '53 bybent-over tabs 59 struck from the flange 51. The: disc 58' islocked'against aninternal shoulder in a dishedmounting member 60, by alocking band or collar cavo-convex accelerating andffocusingggrid thebase. of the mounting, member: 601.

62-carried by Repeller electrode 63comp rises:a cylindrical head portion. 64 having a concaveface 651 andra shank-portion-66.-

Th'e'shank portion. 66 'is .fitted into a ceramic. cylinder 67.

or in any other suitable. manner.

afiixed to the diaphragm 32.

member 72.

A Urshaped metallic. bracket a thin,

to.the:repellerlelectrodet Itwill be -noted'from the con struction:thatthis =el'e'ctr'ode iv-insulatedfrom the "cavity resonator defining'members' and hence, may-'beop'erated at a potential different, fromthat of these elements.

The assembly"comprising the repeller electrode 63,- sleeve fl anddfive'member '72j"which' is coupled to the 61, the mounting memberbeing-.secured to theflange 36- of I th'e'support for the grid3'0l.Thegun-comprises a 6011- 76zis-secured to.theiflan'ge 73.andimounts aninsulating plate or -stripi.77'.again'st Whiclu flexible metallic strapF78-is :locked by a metal eyelet 79.athxed to the repeller leadafv 'Ih'estrap 78; together with a conductor t80i'sealedi to an eyelet 81 on thebase l l by;-a;vitreous-.bead. 82', constitutes the leadiin 'connectiondiaphragm 32 by virtue of the attachment of the sleeve and diaphragm toone another, is bodily movable axially, whereby the diaphragm 32 may beflexed to alter the configuration of the cavity resonator and thus totune it. Such movement of this assembly to tune the resonator isaffected by an electronic tuner unit of such construction that very finetuning may be obtained.

The tuner unit'is'carried byameta'llic support 83 aflixed to one end-ofthe'plate 20 and having outer arms 84an'd an-intermediate arm 85; Itcomprises apairof metallic struts 86 and 87 of the same material, forexample, stainless steel, which are secured at one end to theintermediate arm 85" and 'atthe other end to the collar or flange 74 onthe drive member- 72. The struts-86 a'nd 87 are both provided with alongitudinal flute, and the strut 86 extends substantially normal to thearm 85 and the strut 87 is inclined relative to the strut 86. In orderto locate the tuner assembly accurately, pilot holes 88'are providedinthe arms 34. Piiis exteiidedthroughtheholes 88 permit the asse'i riblytobe' locatedwith extreme accuracy. The pinsrfi'ay 'bepart' ofa' si'nallfixture which-can be withdrawn after the assembly is located and weldedin place.

It is apparent that it" oneor both of the struts are heated, because"ofthe' relative" disposition and expansion of the struts, the ends ofthe struts secured to the flange or collar 74a'nd', heiice, th'e unitaryassembly including. the repelle'r'electrode, will be displaced ilfthjedirection sub stantially'pa rallel'to the longitudinal axisof therepeller electrode. p as the temperature of the struts changes Willbedetermined by the sign-andmagnitude,respectively,of the temperaturechanges." Such temperature changes are accurately controllable in bothsign and magnitude, by utilizing-thestrut 86as theanode of an electronicunit andcontrolling the electron current to this anode.

The electronic unit c'omprises a'pair of insulatingsplates or spacers89' which are supported by a-rnetallio frame or housing 90 havingflanges 9 1 aflixedto the support arms- 81.- Mounted by. the spacers-89in-alignment withthe strut 86 are a cathode 92-ofrectangularcross-section andheatable to emission temperature byaninsulated, folded heater filament 93, and-a recta-ngulargrid 94-carried'by support rods or wires95. The'potentia-l of the g-rid'isappropriately varied to control the electron currentto, and hence, thetemperature of the strut anode' 86; thereby" to tune thecavityresonatorto the desired-frequency:

A thin, flexible strip 96- of high-thermalconductivity material, such ascopper, is connected'at'one end=to the unitary assembly including therepellerelectrode, specifically has an end portion clampedbetvveen thedrive member 72and sleeve71, and has its other end aflixed to the-plate20. The strip 96 functions asaheat bleeder or thermal shunt, to conductheat away from -the drive member 72, =and,-thus, tominimize theeffect-of heatgenerated atthe cavity resonator during operation of thedevice, .upon the tuning-struts. It-tends to hold'the tern peratureuniform over the cavityresonatorsystem, whereby theeffect ofhcating-ofthe-resonator upon the=thermal tuning system is minimized and the tuningsystem-= is quickly, responsive to-changes-in potential'of the controlgrid 94.

Electrical connection to the various electrodes of the reflexoscillatorand th e thermal tuner elementinclude conductors 97'sealed'ineyelets98 on the-base 14 by vitreous beads 99. The conductors 97 extendto terminal pins 100 carried bylanins'ulatin'g base101"which'is providedwith' astem 102 ei1'closin'g metallic "exhaust 'muuta ture 1493, and iscoupledtotheba'se 14by ametallic mountingring" 10 1.

An insulatingwaveguide coupler IDS-encompasses the: cup-like member '15ofi the' envelope IO -and is aflixed thereto by spinning over a section106'of-the wall section'- 12. Due to the insulating character of thecoupler-105, the envelope-10 of the device is separated from theexternal wave guide and hence, may be at a high potential The directionand-amplitude ofdisplacement" without danger of such potential appearingon the external wave guide.

The internal structure as heretofore set forth may be fabricated from aplurality of subassemblies in which the constituent elements areaccurately positioned in prescribed relationship to one another. Theseassemblies are then joined into a unitary mount assembly and accuratelypositioned relative to one another and mounted on the plate 20.

After the base 14 has been sealed to the flanges 12 and 104, theassembly is heated so that the solder pellets in the recesses 22 in theblock 21 melt and braze the block 21 to the wall 11 thereby providing arigid and strong support for the internal elements. A spring 107 aids inholding the block 21 into contact with the wall 11 until the brazing iscompleted. A device is provided by the heretofore set forth structureand methods that is capable of withstanding relatively strong shock andvibration without alteration of the relation of the internal elements orimpairment of operation of the device.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangements of theparts may be made to suit requirements.

What is claimed is:

1. An electron discharge device comprising a cavity resonator, a fixedgrid and a movable grid secured to said resonator and forming a gaptherebetween, a cylindrical electron gun having a heater elementdisposed therein, an insulating strap having a first pair of metallictabs for supporting said heater element and a second pair of metallictabs for securing said strap to said electron gun, means for positioningsaid electron gun concentric with said fixed grid, a repeller electrode,carrying means for said repeller electrode, means for positioning saidrepeller electrode concentric with said movable grid, means forconnecting said carrying means to said movable grid, and thermalresponsive means connected to and supporting said carrying means andresponsive to temperature changes to vary the position of said movablegrid relative to said fixed grid.

2. -An electron discharge device comprising a resonant cavity having afixed grid and a movable grid defining a gap therein, a cylindricalelectron gun having a heater element disposed therein, an insulatingstrap having a first pair of metallic tabs secured thereto forsupporting said heater element and a second pair of metallic tabssecured thereto for securing said strap to said electron gun, means forpositioning said electron gun concentric with said fixed grid, arepeller electrode assembly including a repeller electrode having a headportion and a shank portion, an insulating cylinder surrounding andextending throughout the length of said shank portion, a metal cylindercarrying said insulating cylinder, means for positioning said repellerelectrode assembly concentric with said movable grid, and meansincluding said metal cylinder for varying the position of said movablegrid relative to said fixed grid to tune said device.

References Cited in the file of this patent UNITED STATES PATENTS2,494,693 Ekstrand et al. Jan. 17, 1950 2,513,277 Best July 4, 19502,514,428 Varian et al. July 11, 1950

